Accelerating Mass

The last couple of episodes of In Our Time on Radio 4 have been particularly good. The first was on Pragmatism, not a topic that I initially had much interest in until I discovered that the philosophy of pragmatism, especially that of Charles Peirce, is rather close to what I support – unsurprising, given that it has large similarities to the scientific method. Peirce’s pragmatism seems to be a very solid middle ground between complete relativism (an accusation leveled at some versions of pragmatism) and the idea that there is some immutable ‘truth’ out there. I feel like reading up more on this subject now…

Last week’s programme covered Gravitons. Again, not a terribly inspiring subject – I went off physics when I was about 13 or 14, and never seriously looked back. Still, the guests were unusually good at explaining the subject (much better than the guys who talked about Asteroids a month ago, at least). There was one explanation I liked in particular:

“There might be an analogy between the production of gravitational waves and the production of electronmagnetic waves. Electromagnetic waves – light waves or radio waves – are produced by the acceleration of electrons. If you accelerate an electron, it radiates electromagnetic waves – light. But we know that light can either behave like a wave or like a particle, depending on how you look at it.

“By analogy, accelerating mass can radiate gravitational waves, or perhaps we can think of the gravitational waves in some way of having particle-like properties – gravitons. But the difficulty is, if you want to think of the graviton like a particle, if we can detect gravitational waves, really what we’re detecting is large numbers of gravitons. We won’t see individual gravitons, but it’s kind of equivalent to when you detect radio waves, you don’t detect individual photons, you detect a large number of incoming photons.”

This was by Sheila Rowan, Reader in Physics at Glasgow University, and I thought it was a wonderfully elegant analogy. I assume it’s accurate as well, given that neither of the other physicists there disagreed. It was amusing that throughout the programme, the host kept on referring to Sheila for these sorts of clear explanations of the difficult concepts that were being talked about; to be sure, the other physicists tried to be clear, but they weren’t always successful. I’m looking forward to hearing the final half of the programme on the walk to work tomorrow.

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